1. Field of the Invention
This invention relates to an improvement on a rotating operation part of a camera provided with a moisture- and dust-proof device which is capable of preventing water drops, dust and the like from penetrating into a camera through a rotating operation part thereof.
2. Description of the Prior Art
The automation of cameras of late and the applications of electronics thereto have caused a sudden increase in the number of electric components and parts to be incorporated in cameras. Integrated circuits thus have come to be used for cameras. To facilitate assembling and placing these electric parts and integrated circuits within cameras, they are mounted on substrates. Circuit substrates thus obtained are either inserted in between a pentagonal prism and an upper cover or in the neighborhood thereof or they are arranged between a die casting part of a camera and the bottom cover thereof.
However, the circuit substrates arranged in this manner are vulnerable to external influences because on the upper cover of the camera, there are provided operation members such as film winding and rewinding operation members, which have a shaft extending through holes provided in the upper cover. In the bottom cover, there is also provided a hole for inserting the driving shaft of an electric motor drive unit. It is inevitable that these holes leave some clearances in the upper and bottom covers. Such a clearance is prone to allowing dust, rain water or the like to enter the interior of the camera. When a camera is exposed to rain, for example, water enters the interior of the camera through the clearance existing in the upper cover. The water then tends to cause an electrolytic corrosion of the terminals of a circuit substrate by electrolysing them. If a terminal of the circuit substrate which is provided with an expensive integrated circuit for control is electrolytically corroded in this manner, the camera must be repaired by replacing the whole assembly of the circuit substrate including the expensive integrated circuit. This results in a high cost of repair. Further, intrusion of dust through such a clearance into the camera causes the electromagnet of the camera to generate an insufficient attracting force or it may cause a short circuit between terminals or acceleration of electrolytic corrosion when water enters the interior of the camera.
To solve these problems of conventional cameras, there has been proposed a method in which a rubber ring used at a rotating part of a camera for an antiskid purpose is extended in part for use as a sealing member.
This sealing method of the prior art is shown in sectional view in FIG. 1 of the accompanying drawings as applied to a shutter speed setting dial of a camera. Referring to FIG. 1, an upper cover 1 is secured to a camera body which is not shown. A shutter dial 2 has the shaft thereof interlocked with an internal mechanism of the camera. To improve operability, the shutter dial 2 is provided with an operation rubber ring 3, which is attached to the dial 2. The upper cover 1 is provided with a shaft inserting hole with a guide ring 5 secured to the periphery of the hole by caulking. With this ring 5 serving as a guide, an adjustment washer 4 which is made of metal or a resin material having a lower coefficient of friction than a viscoelastic material is fitted. The operation rubber ring 3 is extended to form an extended part 3a as shown in the drawing. A clearance existing at the operation part is plugged by pushing this part 3a against the adjustment washer 4. In the drawing, reference numeral 6 indicates rain drops. With the operation part arranged as shown in FIG. 1, when the shutter dial 2 is turned, a frictional force between the operation rubber ring 3 and the adjustment washer 4 causes the latter to turn in contact with the upper surface of the upper cover 1 almost as one unified body with the shutter dial 2. FIG. 2 is an enlarged sectional view showing an abutting condition between the adjustment washer 4 and the operation rubber ring 3. As shown, in the above example of the prior art arrangement, the washer 4 and the extended part 3a of the rubber ring 3 are linearly in contact with each other. The linear contact does not give a sufficient sealing effect. Further, it is not desirable for a product such as a camera that should give a high grade impression to have a rubber part exposed to the outside. The use of the rubber part for obtaining a moisture- and dust-proof construction, therefore, degrades the appearance of the camera. The present invention is directed to the elimination of the above stated shortcomings of the prior art arrangement.